A conventional umbrella stretcher system comprises a first main umbrella stretcher (1), a second main umbrella stretcher (2), a rear rib (3), a support stretcher (4), a secondary umbrella stretcher (5) and a flexible rib (6) as shown in FIG. 1. The first main umbrella stretcher (1) and the second main umbrella stretcher (2) and the support stretcher (4) are made of aluminum alloy and have a U-shaped cross section so as to receive other umbrella stretcher members when opening or closing the umbrella. The secondary umbrella stretcher (5) has a flat plate-like aluminum alloy body, which smoothes the operation of the umbrella stretcher system. The reason that these stretcher members are made of alloy aluminum is its light weight, which can provide convenience in use and a suitable strength to support the operation of an umbrella. Such a design does not reveal any significant shortcoming in a normal environment. However, in an area where wind is strong, such a stretcher structure will be easily damaged or broken because the umbrella canopy might be reversed when it bears strong winds The reversal wind force will easily cause the secondary main umbrella stretcher (2) to be damaged or broken by irreversible bending. It ends the service life of the umbrella. This is a major defect of aluminum alloy umbrellas.
In view of the above problem, the primary object of the invention is to provide an aluminum alloy umbrella stretcher structure featured in light weight and improved strength of resisting strong wind, which can be elastically restored without being damaged or broken when the umbrella canopy is reversed. Now the features and advantages of the invention will be described in detail with reference to the accompanying drawings.